Annealing Cold-Formed Stainless Steel Tubes to Reduce Hardness
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Solution Overview
Problem
High-grade austenitic stainless steel tubes with high molybdenum, nickel, and copper content, produced through cold forming, exhibit excessive hardness, making them difficult to handle, transport, and strand for offshore applications.
Innovation Solution
The method involves cold forming austenitic stainless steel tubes, followed by coiling and soft annealing at temperatures between 1,100°C to 1,200°C, allowing the tubes to be transported and stranded more easily by reducing their Rockwell hardness to 90 HRB or less, and then recoiling them onto a reel for further processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If cold forming is used to manufacture stainless steel tubes, then the tubes achieve defined outer and inner diameters with high manufacturing precision, but the hardness of the tubes increases significantly making them difficult to handle and transport
Solution Approach 1:
The patent applies thermal treatment (annealing) to change the physical parameters of the cold-formed stainless steel tubes. By heating the tubes to specific temperatures and then cooling them, the hardness parameter is reduced from the high state created by cold forming to a more manageable state, enabling easier handling and transport while preserving the dimensionally precise geometry achieved during cold forming
2Strength
If cold forming is used to manufacture stainless steel tubes, then the tubes achieve high strength properties, but the hardness increases making stranding difficult
Solution Approach 1:
The patent uses thermal treatment to modify the hardness parameter of the stainless steel tubes without compromising their tensile strength. The annealing process reduces hardness to facilitate stranding operations while maintaining the high strength properties required for offshore applications, thus resolving the contradiction between strength and ease of stranding
3Reliability
If the tubes are produced with high molybdenum, nickel, and copper content, then corrosion resistance is improved, but the manufacturing complexity and cost increase
Solution Approach 1:
The patent applies thermal treatment to modify the physical properties of the high-alloy stainless steel tubes. By controlling the heating and cooling parameters, the process reduces hardness to facilitate handling and stranding while preserving the corrosion resistance provided by the high molybdenum, nickel, and copper content. This resolves the contradiction by adding a relatively simple thermal process step rather than complicating the alloying or forming processes
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the production of stainless steel tubes with reduced hardness, facilitating easier handling, transportation, and stranding, while maintaining their corrosion resistance and tensile strength properties.
Implementation Method 1
annealing the coiled tube after cold forming at a temperature in a range from 1,100° C. to 1,200° C.
Implementation Method 2
soft annealing at temperatures between 1,100°C to 1,200°C, allowing the tubes to be transported and stranded more easily by reducing their Rockwell hardness to 90 HRB or less
Data Source
AI summary
A process for producing a high-grade steel tube includes the steps of: providing a tubular blank of an austenitic high-grade steel, wherein the high-grade steel comprises in weight % no more than 0.02% carbon, no more than 1.0% manganese, no more than 0.03% phosphor, no more than 0.015% sulfur, no more than 0.8% silicon, no more than 17.5% t to 18.5% nickel, no more than 19.5% to 20.5% chromium, no more than 6.0% to 6.5% molybdenum, no more than 0.18% to 0.25% nitrogen, no more than 0.5% to 1.0% copper, and a remainder of iron and unavoidable impurities; and cold-forming the blank into a tube.